A piezoelectric resonator unit that includes a base, a piezoelectric resonator mounted on the base member, and a cover that is bonded to the base and that collectively forms an inner space that accommodates the piezoelectric resonator. The cover includes a top surface that faces the base with the piezoelectric resonator interposed therebetween, and a side wall that extends in a direction that intersects a main surface of the top surface. The piezoelectric resonator unit is designed so that the thickness of the top surface is larger than the thickness of the side wall.